It has long been a feature of many types of compositions, including cosmetic compositions, that they comprise a fragrance oil for the purpose of delivering a pleasant smell. This can improve the overall consumer acceptance of the composition or mask unpleasant odours. In fact, it can be the sole purpose of some compositions to impart a pleasant odour to the skin, hair or other suitable surface.
The fragrance oil(s) used within fragrance compositions usually comprise many different perfume raw materials. Each of these perfume raw materials differs from another by several important properties including individual character, volatility, olfactory detection (known as the odour detection threshold) and the like. By bearing in mind these different properties, and others, fragrance oils, with an overall specific character profile, are developed by blending various perfume raw materials. It is usual that the character is designed to develop, alter and mature over time as the different perfume raw materials evaporate from the surface and are detected by the user. For example, perfume raw materials which have a high volatility are commonly used within a fragrance oil to give light, fresh, fruity, citrus, green or delicate floral characters to the fragrance oil which are detected soon after application. Such materials are usually referred to in the field of fragrances as “top notes”. By way of a contrast, the less volatile perfume raw materials are typically used to give characters such as musk, sweet, balsamic, spicy, woody or heavy floral to the fragrance oil which, although may be detected soon after application, also last for longer. These materials are usually referred to as “middle notes” or “base notes”. Highly skilled perfumers are generally employed to carefully blend perfume raw materials so that the resultant fragrance oils have the desired overall fragrance character profile.
To date, the physical characteristics of the perfume raw materials has been one of the limiting factors for perfumers when designing specific fragrance characters. This is because the volatisation rate of any given ingredient has been mainly related to its boiling point and is therefore out of the control of the perfumer. The result has been that it has only been possible to develop fragrance oils which impart a “top note” character for a short period of time. This is because the top note perfume raw materials are highly volatile and therefore rapidly evaporate from the surface. Therefore, any lasting element of a fragrance has been achieved by using middle and base notes, which in turn restricts the achievable characters. Blending of higher levels of top note perfume raw materials to a fragrance oil does not improve the long lasting nature of the light, fresh, fruity, citrus, green, or delicate floral “top note” fragrance character, but instead may result in a stronger initial burst which still quickly evaporates.
In addition, the physical properties of the surface to which the fragrance composition is applied can also affect the perceived fragrance character. This is because the interaction between the individual perfume raw materials and the surface can also affect the volatisation rate of the fragrance. This is particularly true for human skin, a highly variable surface. For example, consumers with oily skin (e.g., in summer or those living closer to the equator or younger people) often perceive a change in fragrance strength and duration as a result of the fragrance oil becoming dissolved in their skin sebum. Similarly, skin hydration levels can vary between individuals with different skin types (e.g. dry versus normal skin) and/or can vary through the influence of external factors such as weather (skin hydration levels are usually lower in winter), geographical factors (those living at northerly latitudes have lower skin hydration levels than those living nearer the equator) and age. Such varying skin hydration levels can result in dissolution of varying amounts of different fragrance oils, to different extents. Thus, skin hydration levels also impact fragrance performance on the skin. Since skin hydration and sebum levels can vary considerably, this can have a large impact on the consumer perception of a particular fragrance.
It is known that consumer preference for fragrance compositions is mostly driven by the initial character perceived soon after application which often comprises a high level of “top notes”. It is therefore desirable for the user to be able to perceive long lasting initial fragrance character, including long lasting “top note” character. As such, it would be advantageous to be able to tailor a composition, which performs advantageously on different skin types (see above) and which will develop, in a new way, unique fragrance characteristics wherein the release rate of one, or several, well recognised fragrance characters, particularly “top note” fragrance characters, is controlled by factors other than the physical characteristics of the perfume raw materials and the surface (for example, skin type), in order that the fragrance character can be maintained over a substantial period of time. In this way it will be possible to tailor fragrances with unique long lasting, “top, middle and base note” character which consumers with varying surface, especially skin, types will be able to experience. Equally, it is possible to create fragrances with unique long lasting, “top, middle and base note” character, which overcome the variability of fragrance experiences that can result from different surface types.
In the past, many attempts have been made to alter and prolong the volatility profiles of fragrance oils to extend the overall fragrance effect within many types of compositions. For instance, the fragrance oil may be formulated to include a higher proportion of perfume raw materials with a low volatility, i.e. of middle and base note character. However, as discussed above, this restricts the fragrance character that can be achieved over time. Another approach has been to chemically, and reversibly, modify the perfume raw materials to form a pro-perfume compound such as those disclosed in patent applications WO 98/47477; WO 99/43667; WO 98/07405; WO 98/47478; all of which are incorporated herein by reference. The resultant pro-perfumes are not themselves volatile but, after the chemical modification is reversed, the perfume raw material is released and can then evaporate in the usual way. In these applications, the release rate of the perfume raw materials is controlled by the reaction rate for transforming the pro-perfume to perfume raw material. Whilst pro-perfumes can enable the delayed release of specific perfume raw materials, only a restricted range of materials are available and supply can be both limited and expensive due to difficult synthesis and proprietary commercial protection of individual compounds.
Further disclosures have discussed improving the overall longevity of a fragrance by suppressing the evaporation of the fragrance oils themselves by, for example, encapsulating the perfume raw materials (disclosed in JP-A-58/052211, EP-A-303,461); absorbing the materials to a surface, for example, by using carbon or zeolites (disclosed in U.S. Pat. No. 6,033,679); occluding the release of the perfume raw materials, for example, by the formation of a film (disclosed in U.S. Pat. No. 3,939,099); and complexing the perfume raw materials, for example, by using cyclic oligosaccharides. The prior art on this latter method includes JP-A-6/287127 and JP-A-8/176587 which disclose use of hydroxyalkylated cyclodextrins within cosmetic, single phase, alcoholic based solutions or dispersions to sustain the effect of the fragrance; and JP-A-8/183719 and JPA-10/120541 which disclose a combination of cyclodextrin encapsulated fragrance and non encapsulated fragrance within a solid, liquid or aerosol deodorant composition for prolonging the fragrance duration to at least 2 hours, all of which are incorporated herein by reference. Cyclodextrins have also been used with fragrances within cosmetic compositions to improve the solubility of the fragrance oils within the base matrix. The prior art in this area includes JP-A-62/161720 and JP-A-63/192706 which disclose the use of cyclodextrins in fragranced water based compositions. It is expected that these compositions will also have some degree of sustained fragrance release although this is not commented upon in either of these applications.
Whilst the compositions and disclosures of the prior art provide useful teachings for prolonging the fragrance character of a composition as a whole, these approaches still have limitations. Of the cyclic oligosaccharides discussed in the art, cyclodextrins are preferred, especially for fragrance compositions, since they are compatible with, and fully soluble in, a wide range of compositions. However, when used in the traditional way, cyclodextrins interact with a broad range of perfume raw materials including “top, middle and base notes” to form a stable complex which slowly, over time, releases the overall fragrance character. Moreover, these complexes can be so thermodynamically stable that only a very small amount of the complexed fragrance is released over time, sometimes at such a low, and substantially constant, level that it is not noticeable to the user. As such, when used in the traditional way, it is not uncommon for a large amount of the cyclodextrin complexed fragrance to be unused because it remains within the stable complex throughout usage and is unable to evaporate. This results in either a sub-optimal consumer experience or in the manufacturer having to use higher levels of expensive perfume raw materials and/or of entrapment materials (which could lead to poor aesthetics), in order to achieve the desired effect. As such, the prior art does not sufficiently teach how to efficiently release, over time, fragrance, particularly “top note” fragrance characters, from such complexed fragrances such that the composition has a noticeable and long lasting effect. In addition, the prior art does not teach either how to overcome the variability of fragrance experiences that can result from different surface types, in particular different skin types or how to tailor fragrances to optimise the fragrance experience for different surface types.
Surprisingly, it has now been found that release of fragrance from an entrapment structure, on the surface, of at least one fragrance oil and at least one entrapment material, can be improved by the method of destabilising the entrapment structure by providing at least one destabilising material comprising:    i) at least one trigger molecule which preferentially associates with the entrapment material; and/or    ii) at least one release agent which at least partially disrupts (dissolves and/or lyses) the entrapment structure.
Surprisingly, it has also now been found that, within compositions comprising at least one fragrance oil; at least one entrapment material, the at least one fragrance oil and the at least one entrapment material being capable, in use, of forming an entrapment structure on a surface; at least one destabilising material which permits formation of the entrapment structure on the surface and which affects, in use, the decomposition rate of the entrapment structure on the surface; and at least one compatible solvent which does not interfere with formation of the entrapment structure on the surface, a more efficient release of the fragrance oil(s) from the entrapment structure can be achieved.
The method and composition herein increase, in use, the decomposition rate of the entrapment structure on the surface and, thereby, result both in a stronger and more noticeable lasting fragrance character for the user and allow for a possible reduction in the level of fragrance oil(s) that needs to be used within such an entrapment structure without the user perceiving a reduction in fragrance strength. In addition, it has also been surprisingly found that such an at least one destabilising material, when used within any composition comprising at least one fragrance oil and at least one entrapment material, can be used to more efficiently release the fragrance oil from the entrapment structure. Furthermore, it has been found that these destabilising materials can be used to overcome the differences in fragrance perception that can result from difference in surface hydration levels and/or from different surface types.
It is known that fragrance oils and entrapment materials form chemically bonded reversible complexes either within a composition or in situ on the surface. The complex is stabilised by the formation of tertiary interactions such as Van der Waals forces and/or secondary interactions such as hydrogen bonds, between the, or each, fragrance oil and the, or each, entrapment material and the complex exists in equilibrium with uncomplexed fragrance oil(s) and entrapment material(s). On the surface, the complex(es), whether already present in the composition or, alternatively, formed, in situ, on the surface, form an amorphous or, alternatively, regular entrapment structure. In order to break down this entrapment structure, it is necessary to drive the equilibrium towards the free materials.
Whilst not wishing to be bound by theory, it is believed that the present destabilising materials can drive this equilibrium towards the free materials in one of two ways.
The first way is by using release agents which at least partially disrupt (dissolve or lyse) the entrapment structure. This can be achieved by providing dissolution agents such as dissolution solvents, for example, water or the like and/or by increasing the surface hydration levels adjacent the entrapment structure such that the available water at least partially dissolves the entrapment structure. Any materials which are able to cause an increase in the hydration level adjacent to the entrapment structure will be suitable but particularly useful are surface buffering agents, which increase the hydration level by modifying the surface proteins, and compatible and incompatible surfactants which increase the hydration level by improving the surface wetting and by enhancing the water binding. In this way, the present dissolution agents can be used to reduce variability in fragrance perception which can arise as a result of different inherent hydration levels adjacent the entrapment structure and/or to optimise fragrance perception for different surface types. The release agent can, alternatively, act by lysing the entrapment structure. Thus, when the entrapment structure is a pro-perfume, water can hydrolyse the pro-perfume, to release the fragrance. Other solvents can, similarly, lyse the pro-perfume, again to release the fragrance.
The second way that the destabilising materials can drive the entrapment structure to the free state is by providing trigger molecules which preferentially associate with the entrapment material by, for example, actively breaking the tertiary (Van der Waals) and/or secondary (hydrogen bonds) forces that hold the entrapment structure in a thermodynamically stable form. This can be achieved by the use of C1–C15 carboxylic acids, their amides, their esters and their salts which are able to form hydrogen bonds with the, or each, entrapment material, thus thermodynamically driving the breakdown of the entrapment structure. This can also be achieved by the use of incompatible surfactants which, also, preferentially associate with the entrapment material.
If the trigger molecules are to be provided within a composition which also comprises a fragrance oil and an entrapment material, it is necessary to encapsulate the trigger molecules within the composition such that the encapsulated trigger molecules permit formation of the entrapment structure on the surface but, when the trigger molecules are released over time, they then destabilise the entrapment structure by preferentially associating with the entrapment material. If the trigger molecules are to be separately provided, the invention may be enhanced by encapsulating the trigger molecules so that they are released over time, after application of the trigger molecules. Whilst not wishing to be bound by theory, it is believed that, when the trigger molecules are released over time, they delay the release of the fragrance from the entrapment structure. The invention can be still further enhanced by blending the, or each, fragrance oil such that, when it is released from the entrapment structure, it has both the desired characteristics and also the appropriate strength impact. One example is to use high odour impact “top note” perfume raw materials within the, or each, fragrance oil such that the user experiences a noticeable and long lasting “top note” character over time.
It is an object of the present invention to provide destabilising materials which are used to efficiently release the, or each, fragrance oil from the entrapment structure on the surface. It is a further object of this invention to provide destabilising materials for entrapment structures so that the entrapment structures impart long lasting unique fragrance characters that could not be achieved using traditional perfumery, for example, light, fresh, fruity, citrus, green or delicate floral “top note” fragrance character, over a prolonged time and which is independent of the surface hydration level.
It is a still further object of the present invention to provide methods for more efficiently releasing the, or each, fragrance oil from the entrapment structure. These, and other objects of this invention, will become apparent in the light of the following disclosure.